ASA JOURNAL 14/2023

MATERIALS, TOOLS, TECHNIQUES FUNDAMENTAL FACTORS
IN THE DESIGN PROCESS AND WOOD ARCHITECTURAL WORK
135
05-06
แสดงการผุและการทำาลาย
โดยศัตรูทำาลายไม้บริเวณ
เปลือกและกระพี้ของไม้สัก
ขณะที่บริเวณเนื้อไม้ยังคง
สภาพที่ดี
process of transpiration or exchange of water and moisture
with the wood’s surrounding environment continues until
equilibrium with EMC (equilibrium moisture content), which
varies with ambient temperature and relative humidity. This
means that the wood’s moisture content will constantly alter
in accordance with the EMC. This equilibrium moisture content
varies not only with air temperature and relative humidity,
but also with specific environmental factors that influence
the exchange of wood moisture with the environment, such
as wind speed, natural light, application of coatings, etc.
The actual issue with water and moisture affecting wood
materials is not transpiration or exchange of humidity with
the environment, so long as the process is carried out under
optimal conditions. For instance, the cross-sectional area
of wood, which is the open end of the water and nutrientcarrying
vascular and intercellular spaces, can become
more desiccated than the surface area. When there is rapid
dehydration of a large cross-sectional area, the moisture
content of that area decreases, whereas the moisture content
of other parts increases significantly. Unbalanced dimensional
changes in regions with significant humidity differences will
result in fractures known as end checks. But if a coating is
applied that completely obstructs transpiration or moisture
exchange at the end of the wood, the moisture in the wood
will be forced out through the surface, resulting in surface
checks and new issues. Wood drying is recognized as one of
the methods for preparing wood materials to dehumidify (dry)
under controlled conditions in order to prevent injury from
natural transpiration or exchange of humidity processes.
6
In addition to drying in a hot steam cabinet, there are other
methods for reducing moisture in heartwood under controlled
conditions, such as shaded air drying, drying by using air flows
from machinery, etc. Therefore, it can be assumed that the
wood will have an appropriate moisture content after any
pre-treatment in that process, and the process of reducing
the wood’s moisture content must always take into account
the fundamentals of the wood material, such as its size, crosssection,
and length, in order to prevent damage during the
process. It should also be understood that there will be many
problems with size and shape changes when preparing wood
by reducing the moisture under controlled conditions to a level
close to the EMC equilibrium humidity in the environment of
a particular location and then allowing the wood to exchange
natural moisture in that environment for a period of time before
use. The planning, sizing, mounting, and completing operations
that follow this procedure result in improved productivity and
quality of the job.